MTJ element for magnetic random access memory

Abstract

A magnetic random access memory according to an aspect of the present invention comprises a first magnetic layer in which a magnetization state is fixed, a second magnetic layer which has a shape different from that of the first magnetic layer and in which a magnetization state varies in accordance with write data, a non-magnetic layer which is arranged between the first magnetic layer and the second magnetic layer, and a third magnetic layer which surrounds the second magnetic layer.

1. An MTJ element for a random access memory, comprising:
 a first magnetic layer in which a magnetization state is fixed; 
 a second magnetic layer which has a shape different from that of the first magnetic layer and in which a magnetization state varies in accordance with write data; 
 a non-magnetic layer which is arranged between the first magnetic layer and the second magnetic layer; and 
 a third magnetic layer which surrounds all side surfaces of the second magnetic layer and does not surround side surfaces of the first magnetic layer, 
 wherein the first magnetic layer, the second magnetic layer, and the non-magnetic layer are contiguous with each other. 
 
     
     
       2. The MTJ element according to  claim 1 , further comprising an insulating layer which is arranged between the second magnetic layer and the third magnetic layer and separates them from each other. 
     
     
       3. The MTJ element according to  claim 1 , wherein the third magnetic layer is in contact with the second magnetic layer. 
     
     
       4. The MTJ element according to  claim 1 , wherein the first magnetic layer and the non-magnetic layer have the same shape, and the second magnetic layer is arranged on the non-magnetic layer. 
     
     
       5. The MTJ element according to  claim 1 , wherein the first magnetic layer has a square shape, and the second magnetic layer is arranged on the non-magnetic layer and has a square shape smaller than that of the first magnetic layer. 
     
     
       6. The MTJ element according to  claim 5 , wherein the third magnetic layer is arranged on the non-magnetic layer and surrounds side surfaces of the second magnetic layer. 
     
     
       7. The MTJ element according to  claim 6 , further comprising an insulating layer which is arranged between the second magnetic layer and the third magnetic layer and separates them from each other. 
     
     
       8. The MTJ element according to  claim 7 , further comprising a cap layer which is arranged on the second magnetic layer, wherein the insulating layer is formed on the second magnetic layer and side walls of the cap layer. 
     
     
       9. The MTJ element according to  claim 8 , wherein the third magnetic layer surrounds only side surfaces of the second magnetic layer. 
     
     
       10. The MTJ element according to  claim 8 , wherein the third magnetic layer surrounds side surfaces of the second magnetic layer and side surfaces of the cap layer. 
     
     
       11. The MTJ element according to  claim 6 , wherein the third magnetic layer is in contact with the second magnetic layer, and surrounds only side surfaces of the second magnetic layer. 
     
     
       12. The MTJ element according to  claim 6 , further comprising a cap layer which is arranged on the second magnetic layer, wherein the third magnetic layer is in contact with the second magnetic layer and surrounds side surfaces of the second magnetic layer and side surfaces of the cap layer. 
     
     
       13. The MTJ element according to  claim 1 , further comprising an MOS transistor which is arranged directly below the first magnetic layer, the second magnetic layer and the non-magnetic layer. 
     
     
       14. The MTJ element according to  claim 1 , wherein the third magnetic layer comprises a material having magnetic properties different from those of the first magnetic layer and the second magnetic layer.